Guitars and other stringed instruments are tuned by adjusting the tension in the strings. In the case of a guitar, for example, the tension in each string is adjusted individually by turning the tuning heads on the headstock of the guitar. The desired string tension is often obtained by comparing the tone of one string with the tone of another string. The strings get out of tune when the tension in one string changes relative to the tension in one or more of the other strings. One way to help keep a guitar or other stringed instrument in tune, therefore, is to maintain the same relative tension among the strings.